Need part number or alternative solution to plastic stirrup rotation supports

I am having a difficult time finding a part number or alternative solution to broken plastic stirrup supports. These are the black plastic cylindrical components that allow the stirrups to rotate outwards for more natural foot position. The stirrup passes through them giving a rotation axis. These are located inside the table and apparently also act as a stop when pushing the stirrup back into the table. We have a few that have broken. Otherwise the table is fine. Any help is sincerely appreciated!